Our Mini40 trimaran "Secrets" having a good foiling session. Still refinements to make on the foils but we are heading in the right direction. Some onboard footage watching the foils at work, plus a good capsize.
Even motorized hydrofoils struggle with stability. I have great respect for what you have achieved balancing, foiling, sailing and all the disturbances from wind and waves. It looks like great fun too !
No, it's a secret, not a rocket. I think the crew on board is the secret. I never saw anyone on deck. No winches. No helmsman. That's unreal. Maybe it is a rocket?!
I believe one of two things might be causing the foil to stall. First, your foil may be deforming under increased load, thereby changing its angle of attack. Second, and imo the most likely, cavitation is enveloping the foil in a bubble of air. Amazing boat!
Hi, great Video! Very interesting. You were saying that the boat suddenly looses lift and nosedive and you dont know why. I am a Kitefoil racer and we have this problems as well. We call it ventilation. Specially in the upwind course, when we lean hard against the wind we have some air that is coming from the mast down to the wings and then we have a crash. We prevent this problem with a very good sanding of the foil with 800 up to 2500 grid and e cleaning of the foil with window cleaner. When you touch your foil before putting the boat to the water you will have some pollution on the foil and that is why the boat crash. The other important thing is the trailing edge. it has to be sanded with a 30 degree angle. If not, you will have mor turbulences. Simon
Congratulations on the most stable foiling RC multihull I have seen. That leeward foil is always going to be loaded up with significant side pressure, hence to stream of water coming from it.
One of the reasons why the foil could be losing lift so quickly is that o pocket of air got below the foil, usually it isn’t o big problem in bigger boats but in Rc, is probably a big difference. What you could do is make them longer such that they are depose into the water, reducing the risk of the stall. Really great video e amazing boats btw.
Maybe the stall is once foils our out of water the foils weight will increase on the nose.Possibly moving back slightly behind centre of gravity with foil length extended also to achieve even more speed with also a gradual taper to end of foils to reduce drag would help.Some fun you are having thanks for sharing.A bit late, better than never to watch.
Nice boat and session BTW. Would be cool if when the boat gets lift like that it flies stable, then drops back in the water, like a skipping stone or a flying fish. If sail boats could fly.
@@PerthMini40man Nice!! I'm up in Exmouth! - Mate, What would be a decent Radio Transmitter and receiver to get my RC Laser out to around 500m? Hoping you could suggest a good combo as I don't trust the cheap remote and receiver that came with it. Any guidance would be great, Id slip you some prawns if I was closer. Thanks mate.... I lived in Riverside Gardens in Mandurah for 4 years awhile back, Magic place down that way!
Great project!, I was wondering where the main lift foils are located relative to the center of gravity of the fully rigged boat? also do you control the rudder foil rake angle while sailing or is this something you set based on the conditions and see how it performs?
I was wondering that since it is a three-pointer, as the boat heels, the angle of attack of the lee foil changes due to the three-dimensional triangular complex geometry, and this could have an effect on stalling and also causing aeration to dig deeper along the upper vented surface. Would like to try the same model with two rudders one on each float. Adding an anti aeration plate "midway" on the foil would help.
Lift is 95% Newton, not Bernoulli. If you have detachment from your upper camber, that's air migration at atmospheric pressure infiltrating below the waterline of the foil. If you can keep the air from migrating, the water will stick, and you'll get more lift due to the lower pressure on the upper camber.
A bit more weight aft may help and adjust sheet on jib (if nose diving ease sheet on jib) to trim to foil level most foil trimming is with sails to level loading
I'm coming back away from heavy taper ratio foils - they're prone to snap stalling which is what you're seeing here. Think thinner, longer chords are the way to go if you want a foil that behaves.
How about other foil design options? All surfing boards have T-shaped foils instead of passive V-shapes. Those V-s do rise and drop a bit. I call that "nervous." Do you really like that?
When the boat dropped off the foil at near max speed I would lay a bet on cavitation as the cause. As it needs to be fixed I would look to thin the Leading edge and leave the trailing edge mostly alone and try again. I guess the taper is too much and water is separating from the foil by boiling in the negative pressure.
Might the taper design be susceptible to loss of lift caused by an entrained air bubble near the top/rear of the foil? Where the untapered foil could still carry the load, maybe perhaps.
Great idea, How ever in order to cavitation occurs it has to have a really low pressure, and in order to have a really low pressure is has be moving fast. I’ve came acros damage propellers due to cavitation, how ever it was on boats of +30 feet, and propellers about 15 cm as radius, engine at cruising speed about 150 rpm. I think it is extremely unlikely to occurs cavitation in this foil, plus the foil would bend first, due to the low pressure. I think one of the best design for a foil that wouldn’t need much ( if any ) adjust, would be one similar to the foil in the hydropter. As boat gain speed, it gains lift, in gains lift it get get higher above the water, and the it losses lift, losses higher and this cycle goes on until a stable position is reached.
Yes like propellers , i used to work for a propeller manufacturer and designer operating the CAD and have made foils to ride on for foil boards . We had cavitation start at about 15kmph on foils, it often shows as a vibration and evidenced by wear on the areas affected, but once occurring it drops the rider pretty quickly afterward. You find most foils have a limit for speed and then the boat must hold a nose down attitude to hover "level" then soon after it is too much and the boat loses lift. I could feel the vibration through my feet at 15kmph only on a badly made foil and feel the water at 16kmph haha.
Hello this is great!! I`m building also a mini40. what do I have to order from actuonix? 1 or 2 of the PQ12-RC Micro Linear and is that 100: 1? Thank you for your help
Really impressive speed and stability!!! I wonder if you could have a pressure sensor to sense when a foil in in the air by sensing there is no drag on it. Then have that generate a signal that would let out the sheet a tiny bit. Or you could use one of those gyro units they have in beginner rc planes and have that control the foil angles dynamically.
Yes I have contemplated a gyro but reluctant to put more electronics on the boat, increasing the risk of electronic failure due to water getting into the system
Be better if boat balanced foils itself I think via push rod and bell crank system along centre hull and a pick up wand hanging off the front of boat no servos to go wrong perfect... Hope you get along well anyway nice cat!
Ian. - About the sudden stall and drop off from foiling. You might like to experiment with a slight twist in the foils to mitigate immediate stalling of the foil by reduction of the angle of attack at the tip to keep the tip flowing when the area near the root has started to experience loss of flow. Much like a slight twist in the WW2 aircraft wing designed by Mitchell reduced sudden stall in the aircraft he designed subsequent to the sudden stall which crashed one of his Schneider cup aircraft. He late incorporated it into the spitfire which has a noticeable amount of twist that puts the wing root at higher A of A than the tip.
Hello Rob, yes we have a set just as you have described. However we have found that with foils as small as our the boat is incredibly sensitive to gusts and small waves and it is easy to put the boat off its stride. I think that the sudden "snap-stall" when the the boat falls off the foils is caused by a gust hitting the boat and adding extra lateral force on the foils and they simply give up the fight and the boat crashes down. The best way to avoid this is to anticipate the gusts and ease the sails just before the gust hits. Easy to say that.... I am currently testing a spring set up on the boom that the mainsheet attaches to, so that when a gust hits the spring stretches and automatically depowers the mainsail. Tricks like this might help, but need to find the right spring!
@@jazldazl9193 Yes if I can find one of the right strength. But the spring is working quite well and showing promise. Rubber band would be lighter, but will gradually perish in the sunlight
you won't see one from me. Impossible to make one of those at our scale without adding a fin and bulb. The AC40s have computer auto-controlled foils because the crews cannot adjust them fast enough. We would have no chance, and would capsize all over the place, hence the need for a fin and bulb, which rather defeats the object of the entire concept
@@the-naked-sailor design it? build it? The crews are not manually capable of controlling the foils of the current AC or SailGP foils. They are controlled by computers being fed speed and ride-height info. what chance have we got?
@@PerthMini40man.... I'm glad you asked. You seem to know about servos, controllers, sailing, mathematics,.... I know a little about hydraulics, electronics, programming..... and sailing. "Perth mini man" huh? Once again,..... how can I help you?
Just discovered your channel ... really like the servo control of the foils ... perhaps extending the foil and changing the foil profile to that similar to the F50s used in Sail Gp may provide more stable results . Im currently gently working on a scaled version of the f50 Sail Gp Catamaran which utilises two foil rudders and two foils which can be raised independently ... i hope to use a series of micro controllers to eventually create auto-stabalisation , whilst sailing . Very impressed by your post and the foil control system you have developed .
L or T foils are almost impossible for us to use as they have constant lift until they are out of the water, unless you are changing their angle of attack all the time. we have tried wand control for the angle of attack - same as on moths - but this has horrendous drag
It might be stalling, the reason i think that is that your increasing speed but the foil has no way of reducing it's angle of attack. But i only have experience in rc aircraft so don't take my word for it.
I see you've got the foil positioned approximately around the same fore/aft location as on full scale foilers. I'm curious if there would be any stability to be gained by placing them forward of the main beam...basically elogating the two (three?) lifting points (T-rudder and wing foil)?
Hello CAN99. The foils are in fact just forward of the front cross beam. We did try - some years back - putting the foils further forward and it was a complete disaster. First of all, with the foils further from the rudder, the turning circle increased so the tack was slower. But far worse, the foils just acted as 2 sea anchors and the boat was immediately stuck in irons. Could not tack the boat at all, impossible to do a 3-point turn or anything other than drift backwards until it hit the bank. So that is why we have the foils in same position as on full size craft. For sure, if we were never going to tack and make sure we always maintained forward momentum, then the boat would be more stable and probably faster. But we want an all-rounder.
Maybe the vessel is falling off or loosing lift on port tack is because the foil is ventilating. Sucking air down the top low pressure side. This happens when windsufing foiling when riding too high or too much angle of attack.
Best speed we have recorded by GPS is 34kph. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-OciSOzQ8xlk.html&lc=UgzbNf_VH-2YYJMtz7p4AaABAg&feature=em-comments
nice video! why don't designers design bows that will skip or waterski instead of digging in? did you try the upper part of the foil twice as wide to prevent so much lean?
There are sailing scows with bows that promote a waterski effect but they have their limitations, remembering that if a boat is not foiling then its waterlie length dictates the maximum boat speed. Yes our latest boat has foils with a larger area at the kink section. Go here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-12Ao9IPkQG8.html
We have tried that but it makes the boat completely unbalanced and impossible to tack. The boat will go into irons halfway through the tack and you cannot get it out of this situation and so it just drifts backwards onto the shore. It is important to balance the Centre of Effort of the sail area with the centre of lateral resistance of the underwater appendages
I have tried many times, but each time, because the boat is so light, it looses momentum through the tack. However there are a few videos on you tube of boats our size successfully executing a foiling tack so I agree it is possible, I am just good enough to do this yet. Foiling gybes are OK
Yes we have considered it and dropped the idea. The AC75s work because they have fingertip control of the flaps on the foils and can raise and lower the foil arms independently of each other, do to having 6 guys generating power all the way round the course. I do not believe we could recreate such a system that will a) prevent the boat from capsizing and b) control the ride height accurately to within a fe wmm once out of the water. If you scale up our boats and sailing conditions, the gusts we typically experience on small lakes are far more vicious than the real time gusts that these boats experience on open waters.
How about a 'self-adjusting' foil? The deeper the foil is immersed, the more lift it provides and vice versa (up to the point where, when it's about to surface completely, it provides negative lift). This could be done completely without moving parts, simply by shaping the foil appropriately..
That is actually how these foils operate. The faster the boat goes, the more lift the foils produce. The more lift produced, the higher the boat rides above the water, and so the area of foil in the water is reduced, so the boat lowers itself down again until it finds equilibrium. I do not believe that any electronic system can offer the same speed of response, plus I am a keen fane of minimising the amount of electronics on board the boat to reduce the chance of a failure in the system
@@PerthMini40man I'm pretty sure electric servos can react plenty fast enough, but it would need a control loop with sensors, it could not be manually controlled. Some kind of compromise is needed, but I don't think the foils you have will work in larger waves, imagine waves larger than the mast height. You would need active hydrofoils with gyros, accel and hopefully even a camera to see the waves.
Couple of options. 1/ canoe. 2/ let the boat drift upside down until mast hits the bottom. I use a telescopic swimming pool cleaning pole with telescopic fishing rod with line and loop on end to lasso a foil and pull it slowly to the shore, I can reach 25 feet into the lake with this. 3/ fishing rod and line with rubber ball on end to cast over the boat, catch the boat and slowly pull to shore. 4/ use cheap rc electric boat to tow a fishing line out and round the boat and then pull it to shore
We sell the kits of hulls, foils, cross beams and rudder, all painted. Owner supplies rigs and hull fittings including the radio control. Secrets was the 2019 version, we are now selling the jukeBOX which you can watch in our other videos here in youtube
I think the 3 foils should be similar T shape as the rear, because the angle foil looses its grips as the Boat starts to lean and slides to the side and dips... just saying
the fact that the lee foil loses grip as it heels is quite useful as it lets the boat slide sideways and depower. The issue with T foils for all three foils is that due to the rules of the class, I then have to make the boat itself narrower to keep the T foils inside the maximum beam. Plus, it is not easy to develop a ride height control system (most likely a wand system as used by Moths) that can cope with the "small" waves that we have on a lake. Having said that, I am planning to test just such a system in th enext few months, so will see if I can overcome these challenges
I haven't looked into the Mini40 for a decade or so but someone must have played around with gyros controlling the foils by now? I mean, e.g. FliteTest designed their own affordable flight controller for RC planes to help newbies and it's supposedly highly configurable. Or maybe it's against the class rules?
The class rules permit electronics such as gyros but I am not convinced of the benefit of adding more electronics and weight to the boat. I doubt if a servo could respond fast enough to compensate the heel resulting from a gust. In my opinion, it is better to play the sheets and ease the sails slightly, try also to anticipate the gusts by watching the water to windward of the boat. Many of my videos are taken by myself so I only have one hand on the transmitter, with one hand on the video camera so my sailing is often erratic in the videos. I am not controlling the sails
@@PerthMini40man Thanks so much for explaining. I do think the mechanics could be made fast enough, but whether it all would be light enough, I don't know. I tend to think the real challenge would be the programming of the flight controller. But I am just a couch sailor at this point.
Why are the foils placed so far back like normal keels. Why not place foils near the front, so it won't nosedive. Theoretically that brings more longitudinal stability.
If we place the foils any further forward it is impossible to tack the boat, the foils just act as sea anchors and it can be impossibple to reverse trhe boat out of being in irons and it slowly drifts backwards to the lee shore. We have tried . . . . and learnt the hard way. However, the foils are further forward than a conventional keel. Look at the Americas cup foiling monohulls or the SailGP cats - they all have the foils just in front of the mast for the same reason.
